PURPOSE: To realize the A/D converter circuit in which a higher A/D conversion and high precision of the A/D conversion are attained simultaneously through the control of the A/D converter.

CONSTITUTION: The operation of deciding data in a prescribed bit of a DA conversion code is repeated sequentially to each bit from the MSB till the LSB of the DA conversion code depending on the comparison of a comparator circuit section 12 between a voltage resulting in D/A converting a DA conversion code at a D/A converter circuit section 11 and a level of an analog input voltage. Then the A/D converter circuit is provided with an A/D converter control circuit section 13 providing an output of a DA conversion code and latching the DC conversion code decided finally as AD conversion data and with a set period control circuit section 14 controlling a set period in which the DA conversion code is D/A-converted and the result is outputted to a comparator circuit section so that the length of the set period at the LSB conversion is shorter than the length of the set period of the MSB conversion.